The invention relates to an optical fiber connector having an optical fiber piece fixed in the factory in a ferrule, the end of the optical fiber directed outward being provided with a polished surface, and the end directed inward projecting from the ferrule and being connected by thermal welding to the inserted end of an optical fiber to be connected, the ferrule further being fixed in a ferrule holder.
Furthermore, the invention relates to a method for connecting this optical fiber connector to the end of an optical fiber cable.
Two groups of connectors, factory-fitted and field-mounting connectors, are known per se. Very good mechanical and optical properties can be achieved with factory-fitted connectors. It is thereby possible to assemble all types of fibers onto the corresponding connectors. The end faces of the connectors can be provided according to the requirements with all known sections such as, for example, 0xc2x0 PC, APC or UPC. However, it is disadvantageous in this case that this type of connector must be provided with a piece of glass fiber (pigtail) whose length is mostly between 2.5 and 3 meters. The end of this glass fiber piece is then spliced onto the cable to be connected. However, this produces an additional connection, or splice point, which brings with it an additional loss in the transmission link. This connecting point must then additionally be surrounded by an appropriate mechanical guard.
In the case of xe2x80x9cfield-mounting connectorsxe2x80x9d, it is advantageous that the cable to be connected can be connected directly to the connector. This eliminates the additional splice, and also the additional mechanical guard. A plurality of systems of field-mounting connectors are known. In the case of a bonded connector, the optical fiber is bonded in an appropriate receptacle and the end face is subsequently ground and polished. However, with some types of section this grinding and polishing operation is very difficult, or even cannot be executed at all. In the case of what are termed spliced connectors, a synthesis of factory-fitted and field-mounting connectors is undertaken. With these connectors, the difficult part of bonding in the optical fibers, and the grinding of the end face are already carried out in the factory, and the connection, or splicing on of the optical fiber to be connected is then executed on site during the actual field assembly. In principle, this type of connector corresponds to a factory-fitted connector, but no additional outlay is required here to protect the splice point, because the splice is located directly in the connector. Such a type of connector is known by the name of xe2x80x9cFuseLite connectorxe2x80x9d. In the case of such a xe2x80x9cFuseLite connectorxe2x80x9d, use is made of a factory-fitted ferrule with a bonded optical fiber that is ground at the end face and in the case of which an optical fiber piece projects toward the second end face. The optical fiber to be connected is mounted directly onto this optical fiber piece by thermal splicing inside the connector housing. This means that in this region the connector must have appropriate cutouts through which the arc must be guided for welding. This means that in this region the connector must consist of a material of high quality that is exceptionally heat resistant. This material is not permitted to warp at the existing high temperatures, since otherwise it is impossible to achieve the required splice quality. A high quality ceramic, for example zirconium, is used as material for this purpose.
German laid-open application DE 19517750 discloses an optical fiber connector in the case of which the end of an already permanently fixed piece of optical fiber is connected by thermal welding in a connecting sleeve to the end of an optical conductor to be connected. Recessed into the connecting sleeve for this purpose are lateral openings through which the welding electrodes are led up to the splice point.
It is the object of the present invention to create a field mounting optical fiber connector in the case of which the above-named difficulties relating to splicing are simplified, and in the case of which it is also possible to make use in the splice region of materials not of such high quality. The object set is achieved with the aid of an optical fiber connector of the type explained at the beginning, by virtue of the fact that the ferrule with the fixed optical fiber can be detached from the ferrule holder before the thermal welding of the optical fiber end, in that the ferrule is pressed into a receptacle of the ferrule holder after the thermal welding, in that a basic housing with an axially operating compression spring is arranged over the ferrule holder, in that a crimping ring for fixing the stress member of the optical fiber is pressed on the basic housing, in that an anti-kink guard is applied over the cladding of the optical fiber to be connected, and over the end of the basic housing, and in that an outer housing with latching elements is drawn on as a cover.
Furthermore, the object arises with the invention of developing a method for connecting the connector according to the invention to the end of an optical fiber. This object set is achieved with the aid of the method according to the features of claim 5.
Owing to the design of the optical fiber connector according to the invention, it is to be emphasized as a particular advantage by comparison with the prior art that splicing the optical fiber piece held in a ferrule onto the end of the optical fiber to be connected can not be executed inside a connector housing, but separately outside thereof In addition, it is now possible also to make use of a normal optical splicer for the thermal welding of the optical fiber ends. This means that a specially modified splicer that must be tuned to the geometry of the connector housing need not be used, as previously customary, for the splicing. Moreover, the welding takes place outside the ferrule, and so the material of the ferrule is no longer exposed to the high temperatures during the thermal welding operation. After the welding operation, the optical fiber connector is then assembled, the ferrule firstly being pressed into a receptacle in a ferrule holder and thereby fixed exactly in position. Subsequently, the further individual parts of the optical fiber connector, which have previously already been pushed in the appropriate sequence onto the optical fiber to be connected, are positioned over the ferrule and the ferrule holder. This completely eliminates the expensive splicing by welding inside the optical fiber connector, and/or a ferrule specially modified therefor and a splicer also specifically created therefor. The splicing is therefore a routine mounting operation such as is otherwise also carried out in the case of any thermal optical fiber splicing between two optical fiber ends. The design of the optical fiber connector described therefor also simultaneously characterizes the method according to the invention, in accordance with which the optical fiber connector is assembled after the finished thermal welding of the optical fiber ends. It is particularly advantageous in the case of the method that the splicing is performed before the assembly of the optical fiber connector, using the distances and dimensions prescribed by the individual parts. Consequently, all the positions of the individual parts are already prescribed for the assembly at this first operation.